Radical coupling for directed C–C/C–S bond formation in the reaction of Cp*IrS2C2B10H10 with 1-azido-3-nitrobenzene

Abstract

Reactions of half-sandwich complex Cp*IrS2C2B10H10 (1) with 1-azido-3-nitrobenzene (3-NO2C6H4N3, L) upon heating or under light led to new complexes 2-6. Complexes 2 and 3 contain a five-membered cyclometalated ligand arising from C(sp(2))-H activation of the azide ligand L. Complex 4 is a 16 electron species containing a new-generated C-C bond between the azide ligand L and the Cp* unit where C(sp(3))-H activation of the methyl unit occurred. Complexes 5 and 6 contain two types of the ligand which appear in complexes 2, 3 and 4. Further reactions of complexes 5 and 6 with L under more harsh conditions gave rise to the nucleophilic addition products 7 and 8, where ring expansion of the azide ligand at the imido site of complexes 5 and 6 happened. Complexes 2-8 were characterized by NMR, MS, IR, and elemental analysis, and X-ray structural analyses were performed for complexes 2-4 and 6-8. The radical mechanisms for the formation of complexes 2-6 were proposed on the basis of capture experiments by EPR and ESI-MS. And the formation mechanism of complexes 7 and 8 was also suggested.